Reaction kinetics of the addition of atomic sulfur to nitric oxide

The reaction of S(P-3(J)) with NO ((2)Pi) in an Ar bath gas has been studied by the laser photolysis-resonance fluorescence technique over 300-810 K at pressures from 60 to 800 mbar. The observed second-order rate constants are close to the low-pressure limit. Fitting of Troe's formalism to experiment, with an estimated F-cent=0.78 exp(-T/7445) and k(infinity) given subsequently, yields k(0)=(6.2+/-0.6)x10(-33) exp(+(940+/-40)/T) cm(6) molecule(-2) s(-1). Error limits are +/-25%. A theoretical analysis of this value suggests that the average energy transferred during collisions between Ar and the excited intermediate is <DeltaE>=-360(-160)(+90) cm(-1). Over 300-800 K, the high-pressure limit is predicted to be k(infinity)=2.2x10(-10) (T/300)(0.24) cm(3) molecule(-1) s(-1). Doublet and quartet adducts between S and NO were characterized via CBS-QB3 theory. The kinetic data can be rationalized with SNO ((2)A') as the major product, and an ab initio estimate of Delta(f)H(298) for SNO is 176+/-8 kJ mol(-1). (C) 2004 American Institute of Physics.